20moa Base with odd sight in question

[hessmachine]

Ok, I will try to put as much info in about this as.

I just purchased a Rem 700 (.308) to shoot long range (1000 yds). So I installed a weaver 20MOA base and used my 3-9x40 Mil-dot scope I have used on my AR for NRA High Power Matches. It's a "cheaper" Bass Pro Model Scope with approx 25 MOA adjustment total. With this scope, I am able to hold very good groups at 600 yards with my hand loaded 223 match ammo. That being said, I placed my scope which is zeroed at 100 yds for 223 onto my 700 just to see where it was at. To my surprise and befuddlement, at 25 yards (which is all I can shoot indoors without traveling an hour + to an outdoor range) it was dead on. Now I expected to be shooting ~20" high, I guess that shows the lack of long range shooting experience I have.

I read a post about bedding the rail properly, which I did not do. Therefore, I will be doing this process over the next few days. Also, beyond going out and buying a new scope with greater adjustment (its on my Christmas List!), how do I get enough elevation to shoot at 1K? With the current set up, I can get 15MOA elevation with my scope, can someone explain to me what I'm missing?

My understanding was that with a 20MOA base it would automatically set my scope on a downward slope thus giving me an a locked in +20MOA all the time. Thus where my thought was 20" high up close. If you do the ballistics for that ammo and a range of 1k. I need a total of 33.75 MOA adjustment, therefore, I assumed that I would be able to subtract the 20 from my base. Giving me a 13.75 needed from my scope, which I have avalible.

Gun: Remington 700 AAC-SD in .308 Win
Ammo: Perfecta (Ficocchi) 147gr FMJ

 

[hessmachine]

So I think I may have figured out what I'm doing wrong. I was forgetting that 20MOA at 25 yards is not the same as 20MOA at 100 yards.

20MOA @ 100 yds = 21"
20MOA @ 25 yds = 1.3125"

So my assumption of shooting 20" high @25 yds, because of the base was way wrong!!!!

 

[FEENIX]

20 MOA cant + 12.5 MOA (ideally 1/2 of your scope's internal elevation adjustment of 25 MOA) = 32.5 MOA (or thereabouts) of elevation adjustment.

33.75 MOA - 32.5 MOA = 1.25 MOA short at 1K yards

Use your mildot reticle subtensions for the difference, i.e., ...

 

[FearNoWind]

If you want more adjustment and want to keep your light beam closer to center in your scope, try this along with that 20 moa rail:


https://www.youtube.com/watch?v=wcRAX5OLtJE&feature=player_detailpage#t=46

 

[el matador]

20 MOA at 25 yards is about 5.2". One thing I've noticed about scopes and mounts is that they are never perfectly machined or centered with the bore. A 20 MOA rail may be pretty close to 20 MOA, but small variations in the receiver, rings and scope itself may account for 5 MOA or more. I have one gun that "should" have 57 MOA of travel (20 MOA rail, 75 MOA/2 elevation on scope) but in reality I only have about 45 MOA. So really you won't know exactly how much elevation you've got until you get sighted in and then crank your turrets.

25 MOA of total adjustment is very little for a long range scope. Not to mention it's really hard to see at 1000 yards through a cheap scope. There's a reason people around here like Nightforce scopes and the like, they are crystal clear at extended ranges. For the money it's hard to beat a Vortex HS-T or PST. They'll give you great glass and plenty of adjustment to get well beyond 1000 yards with a 20 MOA rail.

 

[7magcreedmoor]

Swap whatever rings you are currently using for a set of Burris Posi-lign rings with the offset inserts. You can get up to an additional 20 MOA, depending on which set of inserts you use. They will also let you zero your scope without using up the internal adjustments. I prefer to use them with an angled rail to dial in the rig so that my optimum shooting range (call it 800 yards) is at the mechanical and optical center of my scope, thus avoiding the distortions and turret variations which can occur as you reach the limits of adjustment. I don't mind shooting close range at the bottom edge, since a 50 to 200 yard shot will let me get away with less precise image quality. I'd much rather optimize the longer shots.

 

[el matador]

Well regardless of which rings and rail you have, a scope with 25 MOA of total adjustment is just not practical for a 1000 yard rifle. Even if you end up hitting right on at 1000 with your scope maxed out you will not be able to get a zero anywhere near the bullseye at 100 yards. 33.75 MOA at 1000 minus 25 MOA means your still 8.75 MOA high with it cranked all the way down. I guess if you are only shooting at things between 600 and 1000 it may work, but still your optics are gonna be lacking. I would forget about trying to squeeze any extra elevation out of the cheap scope and worry about getting a good one first! My 2 cents.